Connes advantages

Equation (5.4) is extremely useful for practical measurements, because it allows a very precise tracking of the moveable mirror. In fact, all modem FT-IR and FT Raman spectrometers use the interference pattern of the monochromatic light of a He-Ne laser (iue-Ne — 633 nm or f = 15800 cm ) in order to control the change in optical path length difference. To emphasize this the reference inter- 

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FTIR advantage (the Connes advantage) turns out perhaps to be the major practical contribution of FTIR to NIRS PAC applications. 

Frequency accuracy (Connes advantage) Because the instrument uses a laser to monitor the position of the moving mirror in the main interferometer, the frequency of the measured spectrum is very accurate. 

A third advantage is proffered by the laser referencing system that affords high wavenumber precision (the Connes advantage [23]), aiding the attain-... 

The use of the He-Ne laser Interferometer to reference the position of the moving mirror Increases the accuracy of frequency determination (Connes advantage) for FTIR. 

Another important advantage of FT-IR spectrometers is their outstanding frequency accuracy (Connes advantage), the basis for all achievements in difference spectroscopy. This accuracy of spectral frequencies is due to the precise and stable collection of the interferogram signal, triggered by the helium—neon laser. An accuracy in wavenumber of better than 0.01 cm can be achieved. 

Connes advantage Wavelength accuracy and precision is extremely good because of the use of a HeNe laser to reference the interferometer... 

Double-modulation FT-IR spectrometry may be considered a type of difference-spectrum measurement (see Section 6.2.3), which utilizes the Connes advantage characteristic of FT-IR spectrometry (i.e., measured wavenumbers are accurate and highly reproducible see Section 4.4.3) the infrared spectra of a sample containing a target material and a reference material are measured independently, and the spectrum of the target material is obtained by calculating the difference between the two spectra. This method is particularly... 

Registration (Connes) advantage with internal wavelength reference (He-Ne laser). 

The Connes advantage claimed for interferometers was that laser referencing would yield much greater wavelength accuracy and reproducibility. The latter was crucial for both signal averaging and spectral subtraction but, as the Perkin-Elmer company had shown, this could almost be matched by dispersives. 

The Connes advantage makes use of the high precision of lasers to measure frequencies very precisely. There are no drawbacks to laser precision except for alignment problems, and most Fourier Transform software also includes calibration routines. 

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